This article stems from an exchange with Pieter Fouche, Senior Lecturer and researcher in the field of prehospital emergency care at the University of Tasmania, who shared on LinkedIn, the publication of his latest work in Resuscitation Plus. The discussion that followed — with contributions from colleagues from different EMS systems — made it clear how much this study deserves an in-depth analysis for the prehospital community.
This article examines the study by Fouche et al., recently published in Resuscitation Plus, which offers a rare minute-by-minute view of post-ROSC physiology in the prehospital phase.
The Problem of the Single Snapshot
Familiar scene. The crew achieves ROSC after a prolonged resuscitation. The patient has a pulse, a blood pressure, a saturation. The numbers are documented, the patient is loaded, transport begins. At the time of handover in the ED, the receiving team gets a single set of vital signs — a snapshot of a moment in a phase that may have lasted 40-60 minutes.
But what happened in between?
Most of what we know about post-ROSC physiology in the prehospital setting comes from exactly this type of data: a single blood pressure at handover, a SpO₂ on arrival. Clinical decisions during transport are guided by intermittent cuff measurements and what the crew manages to communicate verbally. Guidelines tell us to maintain systolic above 90 mmHg, MAP above 65 mmHg, and to avoid hypoxemia. Binary targets — you either meet them or you don't.
A new study published in Resuscitation Plus suggests that this approach is fundamentally incomplete.
The Study: Trajectories, Not Photographs
Fouche et al. (2026) linked recordings from Zoll® monitor-defibrillators with the Victorian Ambulance Cardiac Arrest Registry (VACAR) to create something that had never been done at this scale: minute-by-minute physiological profiles of patients after ROSC from out-of-hospital cardiac arrest.
The study included 3,694 adult OHCA patients with sustained ROSC (defined as pulse present on hospital arrival) managed by Ambulance Victoria between 2019 and 2023. For each patient, the team extracted time-stamped readings of systolic blood pressure, mean arterial pressure, SpO₂, EtCO₂, and respiratory rate from defibrillator files, aligned them to the moment of ROSC, and aggregated them into one-minute intervals.
The numbers are striking in their density: the median number of readings per patient was 201 for heart rate, 97 for SpO₂, and 36 for blood pressure. The median time from ROSC to hospital arrival was 58 minutes.
As Fouche himself wrote in his LinkedIn post: what's new is not that post-ROSC physiology has been studied before — it's the dataset. Linking minute-by-minute Zoll data with the cardiac arrest registry provides a much more precise view of what happens in the early post-ROSC phase compared to the usual single snapshot at handover.
This is not a photograph. It's a movie.
Key Findings: Duration Matters More Than We Think
Blood Pressure
Higher mean and minimum systolic blood pressure values were independently associated with survival to hospital discharge. But the most important finding is not about the threshold — it's about time.
Compared to zero minutes below the SBP threshold of 90 mmHg, patients who spent just 10 minutes in hypotension had their odds of survival nearly halved (adjusted OR 0.58). At 30 minutes, the aOR dropped to 0.44. At 60 minutes, it was 0.38.
The same pattern held for MAP below 65 mmHg: 10 minutes of exposure corresponded to an aOR of 0.56, declining to 0.37 at 60 minutes.
This reframes post-ROSC hemodynamics from a binary threshold problem — "is the patient above 90 systolic?" — to a time-dependent cumulative exposure problem. Each additional minute below threshold carries measurable risk.
Oxygenation
SpO₂ showed a graded relationship with survival: the highest odds were found around 95-100% and decreased significantly below 90%. Again, cumulative time below threshold made the difference: 60 minutes with SpO₂ below 90% corresponded to an aOR of 0.77.
The oxygenation data also capture an important temporal nuance. Many measurements in this cohort were acquired in the very first minutes after ROSC — before fluids or vasopressors had time to act, and before oxygen titration was stable. A low SpO₂ in this context likely reflects disease severity and oxygenation failure despite treatment, not under-titration.
ETCO₂ and Respiratory Rate: Context Markers, Not Targets
The authors are notably cautious regarding ETCO₂ and respiratory rate. Higher mean ETCO₂ values were associated with lower survival, and lower values appeared associated with higher survival — but the authors explicitly warn against interpreting this as a therapeutic target.
Why? Because bag-valve-mask ventilation (without an advanced airway device) was much more frequent in survivors (31.4% vs 2.8% in non-survivors), and BVM ventilation can systematically lower ETCO₂ readings through mask leak. Additionally, airway management was often sequential in the same case — SGA, then ETI — making it impossible to classify ventilation mode minute-by-minute.
This is an important methodological lesson: not all numbers that correlate with outcomes are targets to pursue. ETCO₂ and respiratory rate in this cohort function as contextual markers of the patient's overall status, not as parameters to drive up or down.
The Survival–Neurology Dissociation
Perhaps the most provocative finding is what the data did not show.
While early hemodynamic stability and oxygenation were strongly associated with survival to discharge, their association with good neurological outcome at 12 months was much weaker. Only mean SBP showed a modest positive association with favorable neurological outcome.
The authors interpret this as evidence that early physiological stability is necessary but not sufficient for neurological recovery.
For field crews, the practical message is that early physiological stability appears strongly associated with survival after ROSC, while the association with long-term neurological outcome appears more limited in the data from this study.
What It Means for Prehospital Practice
1. Think in terms of cumulative exposure, not thresholds
The traditional approach is binary: SBP above 90, check. MAP above 65, check. This study argues that the relevant metric is how long the patient remains below these values. Ten minutes of hypotension is not "a brief drop" — it's a measurable reduction in survival odds. This should change how we talk about post-ROSC management: not "what was the last BP?" but "how long has the patient been below target?"
2. The first 5–10 minutes matter disproportionately
The trajectory data show that blood pressure rises during the first 5-10 minutes after ROSC before reaching a plateau. This early window is where many measurements fall — and where interventions can have the greatest impact. It aligns with the practical advice from Jeffrey Bilyk, which emerged in the discussion under Fouche's LinkedIn post: after ROSC, stop, optimize, then move. The race is not to the ambulance door — it's against cumulative physiological insult.
3. The monitoring gap between field and dispatch
There's an irony in this study. The Zoll® defibrillators were recording high-fidelity data the entire time — but these data only became visible retrospectively, for research purposes. In the field, during the actual case, the crew acts on what they can see on the monitor. The dispatch center guiding the crew remotely acts on what the crew manages to communicate verbally — effectively recreating the single snapshot problem this study was designed to overcome.
As defibrillator-to-dispatch data links become technically feasible, work like this provides the strongest argument for prioritizing them. If cumulative exposure determines outcome, then those supporting the crew in real time must be able to see the trajectory, not just hear a number.
4. From retrospective data to prospective improvement: the experience with Zoll Case Review
Speaking of high-fidelity data: for several months now, in our emergency system in Valle d'Aosta, we have implemented the Zoll Case Review package for structured debriefing after cardiac arrests. Having access to this level of granularity in post-event analysis is already changing how our crews understand what happened minute-by-minute — from compression quality to post-ROSC hemodynamic trajectories.
The study by Fouche et al. highlights, however, the logical next step: once you can reliably extract and structure this type of data at scale, it becomes possible to build predictive models. Machine learning algorithms capable of identifying early post-ROSC trajectories that anticipate deterioration before it becomes clinically evident. The transition from retrospective analysis to real-time decision support.
It's a direction that requires structured datasets like that of Ambulance Victoria as a foundation — and tools capable of translating physiological complexity into actionable information for those working under time pressure.
5. The post-ROSC phase is a recovery trajectory, not a stable state
The minute-by-minute data paint the early post-ROSC phase as a dynamic recovery phase — pressures rising, oxygenation stabilizing, CO₂ evolving. This is not a patient "in stable condition." It's a patient in active physiological transition, where the direction and speed of change carry prognostic information that isolated values cannot capture.
Limitations to Consider
This is an observational and retrospective study. It cannot prove that correcting hypotension or hypoxemia causes improved survival — only that they are associated. Therapeutic decisions were at the clinician's discretion and not standardized. Comorbidity data were not available, although sensitivity analyses suggest this is unlikely to change the conclusions. The cohort comes from a single EMS system (Ambulance Victoria) with a specific scope of practice, so generalizability to very different systems requires caution.
The findings on ETCO₂ and respiratory rate, as the authors themselves emphasize, should be interpreted with particular attention to the confounding effect of airway management strategies on these measurements.
The Essential Point
For decades we have measured post-ROSC physiology in snapshots and managed it with thresholds. Fouche et al. demonstrate that we have sacrificed resolution — and that resolution matters. The damage from hypotension and hypoxemia after ROSC accumulates minute by minute, and the tools to measure this accumulation are already attached to the patient.
The question is no longer whether we can capture these data. It's whether we can learn to act on them in real time.
Bibliographic reference:
Fouche PF, Nehme E, Burton S, Flanagan B, Meadley B, Anderson D, Stub D, Nehme Z. High-fidelity minute-level physiologic trajectories after ROSC from linked monitor-defibrillator recordings in out-of-hospital cardiac arrest. Resuscitation Plus (2026). DOI: 10.1016/j.resplu.2026.101286
